A motor vehicle includes a drive train which includes a prime mover or drive source, a gearbox, and a driving wheel. Different gear ratios are engagable in the gearbox in order to adapt a rotational speed of the prime mover to a rotational speed of the driving wheel. The gearbox includes multiple gear sets which may be differently configured and combined with the aid of shift elements. A control device controls the shift elements by way of an open-loop system and, in this way, determines which gear step is engaged, i.e., which step-down gear ratio (or step-up gear ratio) is present between an input side and an output side of the transmission, and determines with the aid of which gear sets in which configuration the step-down gear ratio is achieved. During a changeover from one gear into another gear, usually at least one shift element is disengaged and another shift element is engaged in order to achieve a changeover which is as smooth as possible.
The disengagement and engagement of the shift elements usually takes place according to a control profile which is determined before the open-loop control is carried out and is then statically implemented. This approach is also known as a controlled powershift. Under certain circumstances, within the scope of a gear step changeover, a deviation between the predetermined control profile and the arising extent of disengagement of a shift element controlled by way of an open-loop system may become so great that a comfortable gear step changeover cannot be carried out. Such circumstances may be present, for example, during a coasting gear shift accompanied by a strong brake application or during a load change between a traction load and a coast load during the gear change phase.
One problem addressed by the invention is that of providing an improved technique for the changeover of a gear ratio engaged in a gearbox.